FEEDING BEHAVIOR OF A TROPICAL PREDATOR 

 CYPHOMA GIBBOSUM LINNAEUS 



Charles Birkeland* and Brian D. Gregory 



Department of Zoology, University of Washington 



Seattle, Washington 98105 



ABSTRACT 



Individual Cyphoma gibbosum demonstrate the same feeding 

 preferences as the entire species; we found no evidence 

 that this preference was influenced by previous meals. 

 Cyphoma often leaves a prey individual with apparently 

 little damage and moves on to another. Time spent 

 traveling is less than 17o of time spent on prey. Pre- 

 dation may be far more important in reducing recruit- 

 ment to gorgonacean populations than in affecting sur- 

 vival of adults. Cyphoma lives in the midst of a more- 

 than- adequate food supply. The selectivity in choice 

 of prey exhibited by Cyphoma corroborates this conclu- 

 sion. 



OBJECTIVE 



Several taxa of marine organisms reach their greatest local diversity 

 in coral reef communities. Although the processes producing this 

 diversity are poorly known, predator-prey interactions are implicated 

 by two observations: the experimental demonstration that predators 

 can increase local diversity by preventing the monopolization of 

 limiting resources by superior competitors (Paine, 1966; Harper, 

 1969) , and the greater proportion of species in tropical communities 

 which are predators than in temperate communities (Hiatt and Strasburg 

 1960). Thus, to understand the forces structuring the coral reef 

 community, we look to the factors influencing prey selection by 

 predators. 



The variety of food selected or taken by a predator is affected by 

 two opposing sets of factors. Efficiency increases with speciali- 

 zation; e.g., to digest a wider variety of foods requires a greater 

 variety of enzymes; to produce and maintain these enzymes is expen- 

 sive. A predator should thus limit its diet to those prey that it 

 exploits most efficiently (Emlen, 1966; MacArthur and Pianka, 1966). 

 Germane to this is the demonstration by Provasoli e_t a_l. (1959) of 



*Present Address: Smithsonian Tropical Research Institute 

 P.O. Box 2072, Balboa, Canal Zone 



VI-58 



